Spine distraction implant and method

ABSTRACT

A spine distraction implant alleviates pain associated with spinal stenosis and facet arthropathy by expanding the volume in the spine canal and/or neural foramen. The implant provides a spinal extension stop while allowing freedom of spinal flexion.

This application is a continuation of Ser. No. 09/361,510, filed Jul.27, 1999, which is a continuation of Ser. No. 09/124,203, filed Jul. 28,1998, now U.S. Pat. No. 6,090,112, which is a continuation of Ser. No.08/778,093, filed Jan. 2, 1997 which issued into U.S. Pat. No.5,836,948.

BACKGROUND OF THE INVENTION

As the present society ages, it is anticipated that there will be anincrease in adverse spinal conditions which are characteristic of olderpeople. By way of example, with aging comes increases in spinal stenosis(including but not limited to central canal and lateral stenosis), thethickening of the bones which make up the spinal column and facetarthropathy. Spinal stenosis is characterized by a reduction in theavailable space for the passage of blood vessels and nerves. Painassociated with such stenosis can be relieved by medication and/orsurgery. Of course, it is desirable to eliminate the need for majorsurgery for all individuals and in particular for the elderly.

Accordingly, there needs to be developed procedures and implants foralleviating such condition which are minimally invasive, can betolerated by the elderly and can be performed preferably on anoutpatient basis.

SUMMARY OF THE INVENTION

The present invention is directed to providing a minimally invasiveimplant and method for alleviating discomfort associated with the spinalcolumn.

The present invention provides for apparatus and method for relievingpain by relieving the pressure and restrictions on the aforementionedblood vessels and nerves. Such alleviation of pressure is accomplishedin the present invention through the use of an implant and method whichdistract the spinous process of adjacent vertebra in order to alleviatethe problems caused by spinal stenosis and facet arthropathy and thelike. While the implant and method particularly address the needs of theelderly, the invention can be used with individuals of all ages andsizes where distraction of the spinous process would be beneficial.

In one aspect of the invention, an implant is provided for relievingpain comprising a device positioned between a first spinous process anda second spinous process. The device includes a spinal column extensionstop and a spinal column flexion non-inhibitor.

In another aspect of the invention, the implant is positioned betweenthe first spinous process and the second spinous process and includes adistraction wedge that can distract the first and second spinousprocesses as the implant is positioned between the spinous processes.

In yet another aspect of the present invention, the implant includes adevice which is adapted to increasing the volume of the spinal canaland/or the neural foramen as the device is positioned between adjacentspinous processes.

In yet a further aspect of the present invention, a method is presentedfor relieving pain due to the development of, by way of example only,spinal stenosis and facet arthropathy. The method is comprised of thesteps of accessing adjacent first and second spinal processes of thespinal column and distracting the processes a sufficient amount in orderto increase the volume of the spinal canal in order to relieve pain. Themethod further includes implanting a device in order to maintain theamount of distraction required to relieve such pain.

In yet a further aspect of the invention, the method includes implantinga device in order to achieve the desired distraction and to maintainthat distraction.

In yet a further aspect of the invention, the implant includes a firstportion and a second portion. The portions are urged together in orderto achieve the desired distraction.

Other implants and methods within the spirit and scope of the inventioncan be used to increase the volume of the spinal canal therebyalleviating restrictions on vessels and nerves associated therewith, andpain.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 and 2 depict an embodiment of an implant of the invention whichis adjustable in order to select the amount of distraction required.FIG. 1 depicts the implant in a more extended configuration than doesFIG. 2.

FIGS. 3a and 3 b depict side and end views of a first forked and of theembodiment of FIG. 1.

FIGS. 4a and 4 b depict side sectioned and end views of an interbodypiece of the implant of FIG. 1.

FIGS. 5a and 5 b depict side and end views of a second forked end of theembodiment of FIG. 1.

FIGS. 6, 7, 8, 9 and 10 depict apparatus and method for anotherembodiment of the present invention for creating distraction betweenadjacent spinous processes.

FIGS. 11, 12 and 13 depict yet a further embodiment of the invention forcreating distraction between adjacent spinous processes.

FIGS. 14 and 15 depict a further apparatus and method of an embodimentof the invention for creating distraction.

FIGS. 16, 16 a, and 17 depict yet another embodiment of the presentinvention.

FIGS. 18, 19 and 20 depict yet a further apparatus and method of thepresent embodiment.

FIGS. 21 and 22 depict still a further embodiment of the presentinvention.

FIGS. 23, 24 and 25 depict another embodiment of the present invention.

FIGS. 26, 27 and 28 depict another embodiment of the invention.

FIGS. 29 and 30 depict side elevational views of differently shapedimplants of embodiments of the present invention.

FIGS. 31, 32 and 33 depict various implant positions of an apparatus ofthe present invention.

FIGS. 34 and 35 depict yet another apparatus and method of the presentinvention.

FIGS. 36, 37 and 38 depict three different embodiments of the presentinvention.

FIGS. 39 and 40 depict yet another apparatus and method of an embodimentof the present invention.

FIGS. 41, 42 and 43 depict yet further embodiments of an apparatus andmethod of the present invention.

FIG. 44 is still a further embodiment of an implant of the invention.

FIG. 45 is yet another depiction of an apparatus and method of theinvention.

FIGS. 46 and 47 depict still a further apparatus and method of anembodiment of the invention.

FIGS. 48, 49, 50 and 51 depict yet a further apparatus and method of theinvention.

FIGS. 52, 53, 54, 55 a and 55 b depict another apparatus and method ofthe invention.

FIGS. 56, 57 and 58 depict yet a further apparatus and method of theinvention.

FIGS. 59 and 60 depict still a further embodiment of the invention.

FIG. 61 depict another embodiment of the invention.

FIGS. 62 and 63 depict yet another embodiment of the present invention.

FIGS. 64 and 65 depict still a further embodiment of the presentinvention.

FIG. 66 depicts another embodiment of the invention.

FIGS. 67 and 68 depict yet another embodiment of the present invention.

FIGS. 69, 70, 71 and 71 a depict a further embodiment of the presentinvention.

FIGS. 72 and 73 depict still another embodiment of the invention.

FIGS. 74, 75, 76, 77, and 78 depict still other embodiments of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Embodiment of FIGS. 1-5a, 5 b

A first embodiment of the invention is shown in FIGS. 1-5a, 5 b. Implant20 includes first and second forked ends 22 and 24, each defining asaddle 26, 28 respectively. The forked ends 22, 24 are mated using aninterbody piece 30. As can be seen in FIGS. 3a, 3 b, the first forkedend 22 includes a threaded shaft 32 which projects rearwardly from thesaddle 26. The threaded shaft 32 fits into the threaded bore 34 (FIG.4a) of the interbody piece 30.

The second forked end 24 (FIGS. 5a, 5 b) includes a smooth cylindricalshaft 36 which can fit into the smooth bore 38 of the interbody piece30.

FIG. 1 shows the implant 20 in a fully extended position, while FIG. 2shows the implant in an unextended position. In the unextended position,it can be seen that the threaded shaft 32 of the first forked end 22fits inside the hollow cylindrical shaft 36 of the second forked end 24.

For purposes of implantation between adjacent first and second spinousprocesses of the spinal column, the implant 20 is configured as shown inFIG. 2. The first and second spinous processes are exposed usingappropriate surgical techniques and thereafter, the implant 20 ispositioned so that saddle 26 engages the first spinous process, andsaddle 28 engages the second spinous process. At this point, theinterbody piece 30 can be rotated by placing an appropriate tool or pininto the cross holes 40 and upon rotation, the saddle 26 is movedrelative to the saddle 28. Such rotation spreads apart or distracts thespinous processes with the resultant and beneficial effect of enlargingthe volume of the spinal canal in order to alleviate any restrictions onblood vessels and nerves.

It is noted that this implant as well as the several other implantsdescribed herein act as an extension stop. That means that as the backis bent backwardly and thereby placed in extension the spacing betweenadjacent spinous processes cannot be reduced to a distance less than thedistance between the lowest point of saddle 26 and the lowest point ofsaddle 28. This implant, however, does not inhibit or in any way limitthe flexion of the spinal column, wherein the spinal column is bentforward.

Preferably, such a device provides for distraction in the range of about5 millimeters to about 15 millimeters. However, devices which candistract up to and above 22 millimeters may be used depending on thecharacteristics of the individual patient.

With all the ligaments (such as the superspinous ligament) and tissuesassociated with the spinous processes left intact, the implant 20 can beimplanted essentially floating in position in order to gain the benefitsof the aforementioned extension stop and flexion non-inhibitor. Ifdesired, one of the saddles 26 can be laterally pinned with pin 29 toone of the spinous processes and the other saddle can be looselyassociated with the other spinous processes by using a tether 31 whicheither pierces or surrounds the other spinous process and then isattached to the saddle in order to position the saddle relative to thespinous process. Alternatively, both saddles can be loosely tethered tothe adjacent spinous process in order to allow the saddles to moverelative to the spinous processes.

The shape of the saddles, being concave, gives the advantage ofdistributing the forces between the saddle and the respective spinousprocess. This ensures that the bone is not resorbed due to the placementof the implant 20 and that the structural integrity of the bone ismaintained.

The implant 20 in this embodiment can be made of a number of materials,including but not limited to, stainless steel, titanium, ceramics,plastics, elastics, composite materials or any combination of the above.In addition, the modulus of elasticity of the implant can be matched tothat of bone, so that the implant 20 is not too rigid. The flexibilityof the implant can further be enhanced by providing additional aperturesor perforations throughout the implant in addition to the holes 40 whichalso have the above stated purpose of allowing the interbody piece 30 tobe rotated in order to expand the distance between the saddle 26, 28.

In the present embodiment, it is understood that the spinous processescan be accessed and distracted initially using appropriateinstrumentation, and that the implant 20 can be inserted and adjusted inorder to maintain and achieve the desired distraction. Alternatively,the spinous process can be accessed and the implant 20 appropriatelypositioned. Once positioned, the length of the implant can be adjustedin order to distract the spinous processes or extend the distraction ofalready distracted spinous processes. Thus, the implant can be used tocreate a distraction or to maintain a distraction which has already beencreated.

The placement of implants such as implant 20 relative to the spinousprocess will be discussed hereinbelow with other embodiments. However,it is to be noted that ideally, the implant 20 would be placed close tothe instantaneous axis of rotation of the spinal column so that theforces placed on the implant 20 and the forces that the implant 20places on the spinal column are minimized.

Further, it is noted that during the actual process of installing orimplanting the implant 20, that the method uses the approach ofextending the length of the implant 20 a first amount and then allowingthe spine to creep or adjust to this distraction. Thereafter, implant 20would be lengthened another amount, followed by a period where the spineis allowed to creep or adjust to this new level of distraction. Thisprocess could be repeated until the desired amount of distraction hasbeen accomplished. This same method can be used with insertion toolsprior to the installation of an implant. The tools can be used to obtainthe desired distraction using a series of spinal distraction and spinecreep periods before an implant is installed.

Embodiment of FIGS. 6, 7, 8, 9 and 10

The embodiment of the invention shown in the above FIGS. 6, 7, 8, 9 and10 includes distraction or spreader tool 50 which has first and secondarms 52, 54. Arms 52, 54 are pivotal about pivot point 56 andreleaseable from pivot point 56 in order to effect the implantation ofimplant 58. As can be seen in FIG. 6, in cross-section, the arms 52, 54are somewhat concave in order to cradle and securely hold the firstspinous process 60 relative to arm 52 and the second spinous process 62relative to arm 54. The distraction tool 50 can be inserted through asmall incision in the back of the patient in order to address the spacebetween the first spinous process 60 and the second spinous process 62.Once the tool 50 is appropriately positioned, the arms 52, 54 can bespread apart in order to distract the spinous processes. After this hasoccurred, an implant 58 as shown in FIGS. 8 and 9, or of a design shownin other of the embodiments of this invention, can be urged between thearms 52, 54 and into position between the spinous processes. After thisoccurs, the arms 52, 54 can be withdrawn from the spinous processesleaving the implant 58 in place. The implant 58 is urged into placeusing a tool 64 which can be secured to the implant 58 through athreaded bore 66 in the back of the implant. As can be seen in FIG. 10,the implant 58 includes saddles 68 and 70 which cradle the upper andlower spinous processes 60, 62 in much the same manner as the abovefirst embodiment and also in much the same manner as the individual armsof the tool 50. The saddles as described above tend to distribute theload between the implant and the spinous processes and also assure thatthe spinous process is stably seated at the lowest point of therespective saddles.

Embodiment of FIGS. 11, 12 and 13

Another embodiment of the apparatus and method of the invention is shownin FIGS. 11, 12 and 13. In this embodiment, the spreader or distractiontool 80 includes first and second arms 82, 84 which are permanentlypivoted at pivot point 86. The arms include L-shaped ends 88, 90.Through a small incision, the L-shaped ends 88, 90 can be insertedbetween the first and second spinous processes 92, 94. Once positioned,the arms 82, 84 can be spread apart in order to distract the spinousprocesses. The implant 96 can then be urged between the spinousprocesses in order to maintain the distraction. It is noted that implant96 includes wedged surfaces or ramps 98, 100. As the implant 96 is beingurged between the spinous processes, the ramps further cause the spinousprocesses to be distracted. Once the implant 96 is fully implanted, thefull distraction is maintained by the planar surfaces 99, 101 locatedrearwardly of the ramps. It is to be understood that the cross-sectionof the implant 96 can be similar to that shown for implant 58 or similarto other implants in order to gain the advantages of load distributionand stability.

Embodiments of FIGS. 14, 15, 16, 16 a, and 17

In FIGS. 14 and 15, yet another embodiment of the invention is depicted.In this embodiment, the implant 110 includes first and second conicallyshaped members 112, 114. Member 112 includes a male snap connector 116and member 114 includes a female snap connector 118. With male snapconnector 116 urged into female snap connector 118, the first member 112is locked to the second member 114. In this embodiment, a distraction orspreader tool 80 could be used. Once the spinous process has been spreadapart, an implantation tool 120 can be used to position and snaptogether the implant 110. The first member 112 of implant 110 is mountedon one arm and second member 114 is mounted on the other arm of tool120. The member 112, 114 are placed on opposite sides of the spacebetween adjacent spinous processes. The members 112, 114 are urgedtogether so that the implant 110 is locked in place between the spinousprocesses as shown in FIG. 15. It is to be noted that the implant 110can also be made more self-distracting by causing the cylindricalsurface 122 to be more conical, much as surface 124 is conical, in orderto hold implant 1 10 in place relative to the spinous processes and alsoto create additional distraction.

An alternative embodiment of the implant can be seen in FIGS. 16 and 17.This implant 130 includes first and second members 132, 134. In thisparticular embodiment, the implants are held together using a screw (notshown) which is inserted through countersunk bore 136 and engages athreaded bore 138 of the second member 134. Surfaces 139 are flattened(FIG. 17) in order to carry and spread the load applied thereto by thespinous processes.

The embodiment of implant 130 is not circular in overall outsideappearance, as is the embodiment 110 of FIGS. 14 and 15. In particular,with respect to the embodiment of implant 130 of FIGS. 16 and 17, thisembodiment is truncated so that the lateral side 140, 142 are flattenedwith the upper and lower sides 144, 146 being elongated in order tocapture and create a saddle for the upper and lower spinous processes.The upper and lower sides, 144, 146 are rounded to provide a moreanatomical implant which is compatible with the spinous processes.

If it is desired, and in order to assure that the first member 1 32 andthe second member 134 are aligned, key 148 and keyway 150 are designedto mate in a particular manner. Key 148 includes at least one flattenedsurface, such as flattened surface 152, which mates to an appropriatelyflattened surface 154 of the keyway 150. In this manner, the firstmember is appropriately mated to the second member in order to formappropriate upper and lower saddles holding the implant 130 relative tothe upper and lower spinous processes.

FIG. 16a depicts second member 134 in combination with a rounded noselead-in plug 135. Lead-in plug 135 includes a bore 137 which can fitsnugly over key 148. In this configuration, the lead-in plug 135 can beused to assist in the placement of the second member 134 between spinousprocesses. Once the second member 134 is appropriately positioned, thelead-in plug 135 can be removed. It is to be understood that the lead-inplug 135 can have other shapes such as pyramids and cones to assist inurging apart the spinous processes and soft tissues in order to positionthe second member 134.

Embodiment of FIGS. 18, 19 and 20

The implant 330 as shown in FIG. 18 is comprised of first and secondmating wedges 332 and 334. In order to implant these wedges 332, 334,the spinous processes are accessed from both sides and then a tool isused to push the wedges towards each other. As the wedges are urgedtowards each other, the wedges move relative to each other so that thecombined dimension of the implant 330 located between the upper andlower spinous processes 336, 338 (FIG. 20), increases, therebydistracting the spinous processes. It is noted that the wedges 332, 334include saddle 340, 342, which receiving the spinous processes 336, 338.These saddles have the advantages as described hereinabove.

The first or second wedges 332, 334 have a mating arrangement whichincludes a channel 344 and a projection of 346 which can be urged intothe channel in order to lock the wedges 332, 334 together. The channel334 is undercut in order to keep the projection from separatingtherefrom . Further, as in other devices described herein, a detent canbe located in one of the channel and the projection, with acomplimentary recess in the other of the channel and the projection.Once these two snap together, the wedges are prevented from slidingrelative to the other in the channel 344.

While the above embodiment was described with respect to wedges, thewedges could also have been designed substantially as cones with all thesame features and advantages.

Embodiments of FIGS. 21 and 22

The implant 370 is comprised of first and second distraction cone 372,374. These cones are made of a flexible material. The cones arepositioned on either side of the spinous processes 376, 378 as shown inFIG. 21. Using appropriate tool as shown hereinabove, the distractioncones 372, 374 are urged together. As they are urged together, the conesdistract the spinous processes as shown in FIG. 22. Once this hasoccurred, an appropriate screw or other type of fastening mechanism 380can be used to maintain the position of the distraction cones 372, 374.The advantage of this arrangement is that the implant 370 isself-distracting and also that the implant, being flexible, molds aboutthe spinous processes as shown in FIG. 22.

Embodiments of FIG. 23, 24 and 25

In FIGS. 23 and 24, another embodiment of the implant 170 is depicted.This implant is guided in place using an L-shaped guide 172 which canhave a concave cross-section such as the cross-section 52 of retractiontool 50 in FIG. 6 in order to cradle and guide the implant 170 inposition. Preferably a small incision would be made into the back of thepatient and the L-shaped guide tool 172 inserted between the adjacentspinous processes. The implant 170 would be mounted on the end ofinsertion tool 174 and urged into position between the spinousprocesses. The act of urging the implant into position could cause thespinous processes to be further distracted if that is required. Prior tothe insertion of the L-shaped guide tool 172, a distraction tool such asshown in FIG. 13 could be used to initially distract the spinousprocesses.

Implant 170 can be made of a deformable material so that it can be urgedinto place and so that it can somewhat conform to the shape of the upperand lower spinous processes. This deformable material would bepreferably an elastic material. The advantage of such a material wouldbe that the load forces between the implant and the spinous processeswould be distributed over a much broader surface area. Further, theimplant would mold itself to an irregular spinous process shape in orderto locate the implant relative to spinous processes.

With respect to FIG. 25, this implant 176 can be inserted over a guidewire, guide tool or stylet 178. Initially, the guide wire 178 ispositioned through a small incision to the back of the patient to aposition between the adjacent spinous processes. After this hasoccurred, the implant is threaded over the guide wire 178 and urged intoposition between the spinous processes. This urging can further distractthe spinous processes if further distraction is required. Once theimplant is in place, the guide tool 178 is removed and the incisionclosed. The insertion tools of FIGS. 23 and 24 can also be used ifdesired.

Embodiment of FIGS. 26, 27 and 28

The embodiment shown in FIGS. 26, 27 and 28 uses an implant similar tothat depicted in FIGS. 8 and 9 with different insertion tools. As can beseen in FIG. 26, an L-shaped distraction tool 190 is similar to L-shapeddistraction tool 80 (FIG. 12), is used to distract the first and secondspinous processes 192, 194. After this has occurred, an insertion tool196 is placed between the spinous processes 192, 194. Insertion tool 196includes a handle 198 to which is mounted a square-shaped ring 200.

The distraction tool 190 can be inserted through a small incision in theback in order to spread apart the spinous processes. Through the sameincision which has been slightly enlarged laterally, an upper end 202 ofring 200 can be initially inserted followed by the remainder of the ring200. Once the ring is inserted, the ring can be rotated slightly bymoving handle 198 downwardly in order to further wedge the spinousprocesses apart. Once this has been accomplished, an implant such asimplant 204 can be inserted through the ring and properly positionedusing implant handle 206. Thereafter, the implant handle 206 and theinsertion tool 196 can be removed.

Embodiments of FIGS. 29, 30, 31, 32 and 33

As can be seen in FIGS. 29 and 30, the implants 210, 212, can havedifferent shapes when viewed from the side. These implants are similarto the above-referenced implants 58 (FIG. 8) and 204 (FIG. 28). Theseimplants have cross-sections similar to that shown in FIG. 10 whichincludes saddles in order to receive and hold the adjacent spinousprocesses.

As can be seen in FIGS. 31, 32 and 33, these implants can be placed indifferent positions with respect to the spinous process 214. Preferablyas shown in FIG. 33, the implant 210 is placed closest to the lamina216. Being so positioned, the implant 210 is close to the instantaneousaxis of rotation 218 of the spinal column, and the implant wouldexperience least forces caused by movement of the spine. Thus,theoretically, this is the optimal location for the implant.

As can be seen in FIGS. 31 and 32, the implant can be placed midwayalong the spinous process (FIG. 32) and towards the posterior aspect ofthe spinous process (FIG. 31). As positioned shown in FIG. 31, thegreatest force would be placed on the implant 210 due to a combinationof compression and extension of the spinal column.

Embodiment of FIGS. 34 and 35

Another embodiment of the invention is shown in FIGS. 34 and 35. Inthese figures, implant 220 is comprised of a plurality of individualleaves 222 which are substantially V-shaped. The leaves includeinterlocking indentations or detents 224. That is, each leaf includes anindentation with a corresponding protrusion such that a protrusion ofone leaf mates with an indentation of an adjacent leaf. Also associatedwith this embodiment is an insertion tool 226 which has a blunt end 228which conforms to the shape of an individual leaf 222. For insertion ofthis implant into the space between the spinous processes as shown inFIG. 29 the insertion tool 226 first insert a single leaf 220. Afterthat has occurred, the insertion tool then inserts a second leaf withthe protrusion 224 of the second leaf snapping into correspondingindentation made by the protrusion 224 of the first leaf. This processwould reoccur with third and subsequent leaves until the appropriatespacing between the spinous processes was built up. As can be seen inFIG. 29 the lateral edges 229 of the individual leaves 222 are slightlycurved upwardly in order to form a saddle for receiving the upper andlower spinous processes.

Embodiments of FIGS. 36, 37 and 38

The embodiments of FIGS. 36, 37 and 38 which include implants 230, 232,and 234 respectively, are designed in such a manner so the implant locksitself into position once it is properly positioned between the spinousprocesses. Implant 220 is essentially a series of truncated cones andincludes a plurality of ever expanding steps 236. These steps are formedby the conical bodies starting with the nose body 238 followed therebehind by conical body 240. Essentially, the implant 234 looks like afir tree placed on its side.

The implant 230 is inserted laterally throughout the opening betweenupper and lower spinous processes. The first body 238 causes the initialdistraction. Each successive conical body distracts the spinousprocesses a further incremental amount. When the desired distraction hasbeen reached, the spinous processes are locked into position by steps236. At this point, if desired, the initial nose body 238 of the implantand other bodies 240 can be broken, snapped or sawed off if desired inorder to minimize the size of the implant 230. In order for a portion ofthe implant 230 to be broken or snapped off, the intersection betweenbodies such as body 238 and 240, which is intersection line 242, wouldbe somewhat weaken with the appropriate removal of material. It is notedthat only the intersection lines of the initial conical bodies need tobe so weakened. Thus, intersection line 244 between the bodies whichremain between the spinous processes would not need to be weaker, asthere would be no intention that the implant would be broken off at thispoint.

FIG. 37 shows implant 232 positioned between upper and lower spinousprocesses. This implant is wedge-shaped or triangular shaped incross-sectioned and includes bore pluralities 245 and 246. Through thesebores can be placed locking pins 248 and 250. The triangular orwedged-shaped implant can be urged laterally between and thus distractthe upper and lower spinous processes. Once the appropriate distractionis reached, pins 248, 250 can be inserted through the appropriate boresof the bore pluralities 245 and 246 in order to lock the spinousprocesses in a V-shaped valley formed by pins 248, 250 on the one handand the ramped surface 233, 235 on the other hand.

Turning to FIG. 38, the implant 234 has a triangular-shaped orwedge-shaped body similar to that shown in FIG. 32. In this embodiment,tab 252, 254 are pivotally mounted to the triangular shaped body 234.Once the implant 234 is appropriately positioned in order to distractthe spinous processes to the desired amount, the tabs 252, 254 rotateinto position in order to hold the implant 234 in the appropriateposition.

Embodiment of FIGS. 39 and 40

In the embodiment of FIGS. 39 and 40, cannula 258 is inserted through asmall incision to a position between upper and lower spinous processes.Once the cannula is properly inserted, an implant 260 is pushed throughthe cannula 258 using an insertion tool 262. The implant 260 includes aplurality of ribs or indentation 264 that assist in positioning theimplant 260 relative to the upper and lower spinal processes. Once theimplant 260 is in position, the cannula 258 is withdrawn so that theimplant 260 comes in contact with and wedges between the spinousprocesses. The cannula 258 is somewhat conical in shape with the noseend 266 being somewhat smaller than the distal end 268 in order toeffect the insertion of the cannula into the space between the spinousprocesses.

Further, a plurality of cannula can be used instead of one, with eachcannula being slightly bigger than one before. In the method of theinvention, the first smaller cannula would be inserted followed bysuccessively larger cannula being placed over the previous smallercannula. The smaller cannula would then be withdrawn from the center ofthe larger cannula. Once the largest cannula is in place, and theopening of the skin accordingly expanded, the implant, which isaccommodated by only the larger cannula, is inserted through the largercannula and into position.

Embodiments of FIGS. 41, 42 and 43

The precurved implant 270 in FIGS. 41 and 42, and precurved implant 272in FIG. 43 have common introduction techniques which includes a guidewire, guide tool, or stylet 274. For both embodiments, the guide wire274 is appropriately positioned through the skin of the patient and intothe space between the spinous processes. After this is accomplished, theimplant is directed over the guide wire and into position between thespinous processes. The precurved nature of the implant assist in (1)positioning the implant through a first small incision in the patient'sskin on one side of the space between two spinous processes and (2)guiding the implant toward a second small incision in the patient's skinon the other side of the space between the two spinous processes. Withrespect to the implant 270, the implant includes a conical introductionnose 276 and a distal portion 278. As the nose 276 is inserted betweenthe spinous processes, this causes distraction of the spinous processes.Break lines 280, 282 are established at opposite sides of the implant270. Once the implant is properly positioned over the guide wire betweenthe spinous processes, the nose portion 276 and the distal portion 278can be broken off along the break lines, through the above twoincisions, in order to leave the implant 270 in position.

Although only two break lines 280, 282 are depicted, multiple breaklines can be provided on implant 270 so that the implant can continue tobe fed over the guide wire 278 until the appropriate width of theimplant 270 creates the desired amount of distraction. As describedhereinabove, the break lines can be created by perforating or otherwiseweakening the implant 270 so that the appropriate portions can besnapped or sawed off.

With respect to the precurved implant 272, this implant is similar indesign to the implant 230 shown in FIG. 36. This implant 272 in FIG. 47,however, is precurved and inserted over a guide wire 274 to a positionbetween the spinous processes. As with implant 230 in FIG. 43, once theappropriate level of this distraction has been reached and if desired,sections of the implant 272 can be broken, snapped or sawed off asdescribed hereinabove in order to leave a portion of the implant wedgedbetween the upper and lower spinous processes.

Embodiment of FIG. 44

A further embodiment of the invention is shown in FIG. 44. Thisembodiment includes a combination insertion tool and implant 290. Theinsertion tool and implant 290 is in the shape of a ring which is hingedat point 292. The ring is formed by a first elongated and conicallyshaped member 294 and a second elongated and conically shaped member296. Members 294 and 296 terminate in points and through the use ofhinge 292 are aligned and meet. Through similar incisions on both sidesof the spinous processes, first member and second member are insertedthrough the skins of the patient and are mated together between thespinous processes. After this has occurred, the implant 290 is rotated,for example clockwise, so that increasingly widening portions of thefirst member 292 are used to distract the first and second spinousprocesses. When the appropriate level of distraction has occurred, theremainder of the ring before and after the section which is locatedbetween the spinous processes can be broken off as taught hereinabove inorder to maintain the desired distraction. Alternatively, with a smallenough ring, the entire ring can be left in place with the spinousprocesses distracted.

Embodiment of FIG. 45

In FIG. 45, the implant 300 is comprised of a plurality of rods orstylets 302 which are inserted between the upper and lower spinousprocesses. The rods are designed much as described hereinabove so thatthey may be broken, snapped or cut off. Once these are inserted and theappropriate distraction has been reached, the stylets are broken off anda segment of each stylet remains in order to maintain distraction of thespinous process.

Embodiment of FIGS. 46 and 47

Implant 310 of FIGS. 46 and 47 is comprised of a shape memory materialwhich coils upon being released. The material is straightened out in adelivery tool 312. The delivery tool is in position between upper andlower spinous processes 314, 316. The material is then pushed throughthe delivery tool. As it is released from the delivery end 318 of thedelivery tool, the material coils, distracting the spinous processes tothe desired amount. Once this distraction has been achieved, thematerial is cut and the delivery tool removed.

Embodiments of FIGS. 48, 49, 50 and 51

As can be seen in FIG. 48, the implant 320 is delivered between upperand lower spinous processes 322 and 324, by delivery tool 326. Once theimplant 320 is in place between the spinous processes, the delivery toolis given a 90° twist so that the implant goes from the orientation asshown in FIG. 49, with longest dimension substantially perpendicular tothe spinous processes, to the orientation shown in FIG. 50 where thelongest dimension is in line with and parallel to the spinous processes.This rotation causes the desired distraction between the spinousprocesses. Implant 320 includes opposed recesses 321 and 323 located atthe ends thereof. Rotation of the implant 320 causes the spinousprocesses to become lodged in these recesses.

Alternatively, the insertion tool 326 can be used to insert multipleimplants 320, 321 into the space between the spinous processes 322, 324(FIG. 51). Multiple implants 320, 321 can be inserted until theappropriate amount of distraction is built up. It is to be understood inthis situation that one implant would lock to another implant by use of,for example, a channel arrangement wherein a projection from one of theimplants would be received into and locked into a channel of the otherimplant. Such a channel arrangement is depicted with respect to theother embodiment.

Embodiment of FIGS. 52, 53, 54, 55 a and 55 b

The embodiment of FIGS. 52 through 55b is comprised of a fluid-filleddynamic distraction implant 350. This implant includes a membrane 352which is placed over pre-bent insertion rod 354 and then insertedthrough an incision on one side of the spinous process 356. The bentinsertion rod, with the implant 350 thereover, is guided betweenappropriate spinous processes. After this occurs, the insertion rod 354is removed leaving the flexible implant in place. The implant 350 isthen connected to a source of fluid (gas, liquid, gel and the like) andthe fluid is forced into the implant causing it to expand as shown inFIG. 54, distracting the spinal processes to the desired amount. Oncethe desired amount of distraction has occurred, the implant 350 isclosed off as is shown in FIG. 55a. The implant 350 being flexible, canmold to the spinous processes which may be of irregular shape, thusassuring positioning. Further, implant 350 acts as a shock absorber,damping forces and stresses between the implant and the spinousprocesses.

A variety of materials can be used to make the implant and the fluidwhich is forced into the implant. By way of example only, viscoelasticsubstances such as methylcellulose, or hyaluronic acid can be used tofill the implant. Further, materials which are initially a fluid, butlater solidify, can be inserted in order to cause the necessarydistraction. As the materials solidify, they mold into a custom shapeabout the spinous processes and accordingly are held in position atleast with respect to one of two adjacent spinous processes. Thus, itcan be appreciated that using this embodiment and appropriate insertiontools the implant can be formed about one spinous process in such amanner that the implant stays positioned with respect to that spinousprocess (FIG. 55b). With such an embodiment, a single implant can beused as an extension stop for spinous process located on either side,without restricting flexion of the spinal column.

It is to be understood that many of the other implants disclosed hereincan be modified so that they receive a fluid in order to establish andmaintain a desired distraction much in the manner as implant 350receives a fluid.

Embodiment of FIGS. 56, 57 and 58

The implant 360 as shown in FIG. 56 is comprised of a shape memorymaterial such as a plastic or a metal: A curved introductory tool 362 ispositioned between the appropriate spinous processes as describedhereinabove. Once this has occurred, bore 364 of the implant is receivedover the tool. This act can cause the implant to straighten out. Theimplant is then urged into position and thereby distracts the spinousprocesses. When this has occurred, the insertion tool 362 is removed,allowing the implant to assume its pre-straightened configuration and isthereby secured about one of the spinous processes. Such an arrangementallows for an implant that is an extension stop and does not inhibitflexion of the spinous column. Alternatively, the implant can betemperature sensitive. That is to say that the implant would be morestraightened initially, but become more curved when it was warmed by thetemperature of the patient's body.

Embodiments of FIGS. 59 and 60

In this embodiment, the implant 380 is comprised of a plurality ofinterlocking leaves 382. Initially, a first leaf is positioned betweenopposed spinous processes 384, 386. Then subsequently, leafs 382 areinterposed between the spinous processes until the desired distractionhas been built up. The leaves are somewhat spring-like in order toabsorb the shock and can somewhat conform to the spinous processes.

Embodiment of FIG. 61

The implant 390 of FIG. 61 includes the placement of shields 392, 394over adjacent spinous processes 396, 398. The shields are used toprevent damage to the spinous processes. These shields include apertureswhich receives a self-tapping screw 400, 402. In practice, the shieldsare affixed to the spinous processes and the spinous processes aredistracted in the appropriate amount. Once this has occurred, a rod 404is used to hold the distracted position by being screwed into each ofthe spinous processes through the aperture in the shields using thescrews as depicted in FIG. 61.

Embodiment of FIGS. 62 and 63

Implant 410 of FIGS. 62, 63 is comprised of first and second members412, 414 which can be mated together using an appropriate screw andthreaded bore arrangement to form the implant 410. Main member 412 andmating member 414 form implant 410. Accordingly, the implant 410 wouldhave a plurality of members 414 for use with a standardized first member412. FIGS. 62 and show different types of mating members 414. In FIG.62, the mating member 414 includes projections 416 and 418 which actlike shims. These projections are used to project into the space ofsaddles 420, 422 of the first member 412. These projections 416, 418 canbe of varying lengths in order to accommodate different sizes of spinousprocesses. A groove 424 is placed between the projections 416, 418 andmates with an extension 426 of the first member 412.

As shown in FIG. 63, the projections of the embodiment shown in FIG. 62are removed and recesses 428, 430 are substituted therefor. Theserecesses expand the area of the saddles 420, 422 in order to accommodatelarger spinous processes.

Embodiment of FIGS. 64. 65 and 66

The embodiments of FIGS. 64, 65 and 66 are similar in design and conceptto the embodiment of FIGS. 62 and 63. In FIG. 64, the implant 500includes the first and second members 502, 504. These members can besecured together with appropriate screws or other fastening means astaught in other embodiments. Implant 500 includes first and secondsaddles 506, 508 which are formed between the ends of first and secondmembers 502, 504. These saddles 506, 508 are used to receive and cradlethe adjacent spinous processes. As can be seen in FIG. 64, each saddle506, 508 is defined by a single projection or leg 510, 512, whichextends from the appropriate first and second members 502, 504. Unlikethe embodiment found in FIGS. 62 and 63, each of the saddles is definedby only a single leg as the ligaments and other tissues associated withthe spinous processes can be used to ensure that the implant is held inan appropriate position. With the configuration of FIG. 64, it is easierto position the implant relative to the spinous processes as each saddleis defined by only a single leg and thus the first and second memberscan be more easily worked into position between the various tissues.

In the embodiment of FIG. 65, the implant 520 is comprised of a singlepiece having saddles 522 and 524. The saddles are defined by a singleleg 526, 528 respectively. In order for this implant 520 to bepositioned between the spinous processes, an incision is made betweenlateral sides of adjacent spinous processes. The single leg 526 isdirected through the incision to a position adjacent to an oppositelateral side of the spinous process with the spinous process cradled inthe saddle 522. The spinous processes are then urged apart until saddle524 can be pivoted into position into engagement with the other spinousprocess in order to maintain the distraction between the two adjacentspinous processes.

The embodiment of FIG. 66 is similar to that of FIG. 65 with an implant530 and first and second saddles 532 and 534. Associated with eachsaddle is a tether 536, 538 respectively. The tethers are made offlexible materials known in the trade and industry and are positionedthrough bores in the implant 530. Once appropriately positioned, thetethers can be tied off. It is to be understood that the tethers are notmeant to be used to immobilize one spinous process relative to theother, but are used to guide motion of the spinous processes relative toeach other so that the implant 530 can be used as an extension stop anda flexion non-inhibitor. In other words, the saddles 532, 534 are usedto stop spinal column backward bending and extension. However, thetethers do not inhibit forward bending and spinal column flexion.

Embodiments of FIGS. 67, 68

The implant 550 is Z-shaped and includes a central body 552 and firstand second arms 554, 556, extending in opposite directions therefrom.The central body 552 of the implant 550 includes first and secondsaddles 558 and 560. The first and second saddles 558 and 560 wouldreceive upper and lower spinous processes 562, 568. The arms 554, 556are accordingly located adjacent the distal end 566 (FIG. 68) of thecentral body 552. The first and second arms 554, 556, act to inhibitforward movement, migration or slippage of the implant 550 toward thespinal canal and keep the implant in place relative to the first andsecond spinal processes. This prevents the implant from pressing down onthe ligamentum flavum and the dura. In a preferred embodiment, thecentral body would have a height of about 10 mm with each of the arms554, 556 have a height of also about 10 mm. Depending on the patient,the height of the body could vary from about less than 10 mm to aboutgreater than 24 mm. As can be seen in FIGS. 67 and 68, the first andsecond arms 554, 556 are additionally contoured in order to accept theupper and lower spinous processes 556, 558. In particular, the arms 554,556 as can be seen with respect to arm 554 have a slightly outwardlybowed portion 568 (FIG. 68) with a distal end 570 which is slightlyinwardly bowed. This configuration allows the arm to fit about thespinous process with the distal end 570 somewhat urged against thespinous process in order to guide the motion of the spinous processrelative to the implant. These arms 554, 556 could if desired to be mademore flexible than the central body 552 by making arms 554, 556 thinand/or with perforations, and/or other material different than that ofthe central body 550. As with the last embodiment, this embodiment canbe urged into position between adjacent spinous processes by directingan arm into a lateral incision so that the central body 552 can befinally positioned between spinous processes.

Embodiment of FIGS. 69, 70, 71 and 71 a

FIGS. 69, 70 and 71 are perspective front, end, and side views ofimplant 580 of the invention. This implant includes a central body 582which has first and second saddles 584, 586 for receiving adjacentspinous processes. Additionally, the implant 580 includes first andsecond arms 588 and 590. The arms, as with the past embodiment, preventforward migration or slippage of the implant toward the spinal canal.First arm 588 projects outwardly from the first saddle 584 and secondarm 590 projects outwardly from the second saddle 586. In a preferredembodiment, the first arm 588 is located adjacent to the distal end 600of the central body 582 and proceeds only partly along the length of thecentral body 582. The first arm 588 is substantially perpendicular tothe central body as shown in FIG. 70. Further, the first arm 588, aswell as the second arm 590, is anatomically rounded.

The second arm 590, projecting from second saddle 586, is locatedsomewhat rearward of the distal end 600, and extends partially along thelength of the central body 582. The second arm 590 projects at acompound angle from the central body 582. As can be seen in FIGS. 70 and71, the second arm 590 is shown to be at about an angle of 45° from thesaddle 586 (FIG. 70). Additionally, the second arm 590 is at an angle ofabout 45° relative to the length of the central body 580 as shown inFIG. 71. It is to be understood that other compound angles are withinthe spirit and scope of the invention as claimed.

In a preferred embodiment, the first and second arms 588, 590 have alength which is about the same as the width of the central body 582.Preferably, the length of each arm is about 10 mm and the width of thecentral body is about 10 mm. However, the bodies with the widths of 24mm and greater are within the spirit and scope of the invention, alongwith first and second arms ranging from about 10 mm to greater thanabout 24 mm. Further, it is contemplated that the embodiment couldinclude a central body having a width of about or greater than 24 mmwith arms being at about 10 mm.

It is to be understood that the embodiment of FIGS. 69, 70 and 71 aswell as the embodiment of FIGS. 67 and 68 are designed to preferably bepositioned between the L4-L5 and the L5-S1 vertebral pairs. Theembodiment of FIGS. 69, 70, 71 is particularly designed for the L5-S1position with the arms being designed to conform to the sloping surfacesfound therebetween. The first and second arms are thus contoured so thatthey lie flat against the lamina of the vertebra which has a slightangle.

The embodiment of FIG. 69, 70, and 71 as with the embodiment of FIGS. 67and 68 is Z-shaped in configuration so that it may be inserted from onelateral side to a position between adjacent spinous processes. A firstarm, followed by the central body, is guided through the space betweenthe spinous processes. Such an arrangement only requires that a incisionon one side of the spinous process be made in order to successfullyimplant the device between the two spinous processes.

The implant 610 of FIG. 71a is similar to that immediately above withthe first arm 612 located on the same side of the implant as the secondarm 614. The first and second saddle 616, 618 are slightly modified inthat distal portion 620, 622 are somewhat flattened from the normalsaddle shape in order to allow the implant to be positioned between thespinous processes from one side. Once in position, the ligaments andtissues associated with the spinous processes would hold the implantinto position. Tethers also could be used if desired.

Embodiment of FIGS. 72, 73

Implant 630 is also designed so that it can be inserted from one side ofadjacent spinous processes. This insert 630 includes a central body 632with the first and second arms 634, 636 extending on either sidethereof. As can be seen in FIG. 72, a plunger 638 is positioned toextend from an end of the central body 632. As shown in FIG. 72, theplunger 638 is fully extended and as shown in FIG. 73, the plunger 638is received within the central body 632 of the implant 630. With theplunger received into the implant 632, the third and fourth arms orhooks 640, 642 can extend outwardly from the central body 632. The thirdand fourth arms or hooks 640, 642 can be comprised of a variety ofmaterials, such as for example, shape memory metal materials ormaterials which have a springy quality.

For purposes of positioning the implant 630 between adjacent spinousprocesses, the plunger 638 is pulled outwardly as shown in FIG. 72. Thecentral body 632 is then positioned between adjacent spinous processesand the plunger 638 is allowed to move to the position of FIG. 73 sothat the third and fourth arms 640, 642 can project outwardly from thecentral body 632 in order to hold the implant 630 in position betweenthe spinous processes.

Plunger 638 can be spring biased to the position as shown in FIG. 73 orcan include detents or other mechanisms which lock it into thatposition. Further, the third and fourth arms themselves, as deployed,can keep the plunger in the position as shown in FIG. 73.

Embodiments of FIGS. 74, 75, 76, 77, and 78

Other embodiments of the invention are shown in FIGS. 74 through 78.FIGS. 74, 75 and 76 disclose implant 700. Implant 700 is particularlysuited for implantation between the L4-L5 and L5-S1 vertebra. As can beseen in FIG. 74, the implant 700 includes a central body 702 which has abore 704 provided therein. Bore 704 is used in order to adjust themodulus of elasticity of the implant so that it is preferablyapproximately two times the anatomical load placed on the vertebra inextension. In other words, the implant 700 is approximately two timesstiffer than the normal load placed on the implant. Such an arrangementis made in order to ensure that the implant is somewhat flexible inorder to reduce potential resorption of the bone adjacent to theimplant. Other modulus values can be used and be within the spirit ofthe invention.

Implant 700 includes first and second saddle 706, 708 which are used toreceive and spread the load from the upper and lower spinous processes.The saddle 706 is defined by first and second arms 710 and 712. Thesecond saddle 708 is defined by third and fourth arms 714 and 716. Ascan be seen in FIG. 74, the first arm 710, in a preferred embodiment, isapproximately two times the length of the body 702 with the second armbeing approximately less than a quarter length of the body. Third arm714 is approximately one times the length of the body 702 with thefourth arm 716 being, in this preferred embodiment, approximately oneand a half times the length of the body 702. The arms are designed insuch a way that the implant (1) can be easily and conveniently insertedbetween the adjacent spinous processes, (2) will not migrate forwardlytoward the spinal canal, and (3) will hold its position through flexionand extension as well as lateral bending of the spinal column.

First arm 710 is in addition designed to accommodate the shape of thevertebra. As can be seen in FIG. 74, the first arm 710 becomes narroweras it extends away from the body 702. The first arm 710 includes asloping portion 718 followed by a small recess 720 ending in a roundedportion 722 adjacent to the end 724. This design is provided toaccommodate the anatomical form of for example the L4 vertebra. It is tobe understood that these vertebra have a number of surfaces at roughly30° angles and that the sloping surfaces of this embodiment and theembodiments shown in FIGS. 77 and 78 are designed to accommodate thesesurfaces. These embodiments can be further modified in order toaccommodate other angles and shapes.

The second arm 712 is small so that it is easy to insert between thespinous processes, yet still define the saddle 706. The fourth arm 716is larger than the third arm 714, both of which are smaller than thefirst arm 710. The third and fourth arms are designed so that theydefine the saddle 706, guide the spinous processes relative to theimplant 700 during movement of the spinal column, and yet are of a sizewhich makes the implant easy to position between the spinous processes.

The procedure, by way of example only, for implanting the implant 700can be to make an incision laterally between two spinous processes andthen initially insert first arm 710 between the spinous processes. Theimplant and/or appropriate tools would be used to distract the spinousprocesses allowing the third leg 714 and the central body 702 to fitthrough the space between the spinous processes. The third leg 714 wouldthen come to rest adjacent the lower spinous processes on the oppositeside with the spinous processes resting in the first and second saddle706, 708. The longer fourth leg 716 would then assist in the positioningof the implant 700.

FIG. 77 includes an implant 740 which is similar to implant 700 and thushave similar numbering. The saddle 706, 708 of implant 740 have beencantered or sloped in order to accommodate the bone structure between,by way of example, the L4-L5 and the L5-S1 vertebra. As indicated above,the vertebra in this area have a number of sloping surfaces in the rangeof about 30°. Accordingly, saddle 706 is sloped at less than 30° andpreferably about 20° while saddle 708 is sloped at about 30° andpreferably more than 30°.

The implant 760 as shown in FIG. 78 is similar to implant 700 in FIG. 74and is similarly numbered. Implant 760 includes third and fourth legs714, 716 which have sloping portions 762, 764 which slope toward ends766, 768 of third and fourth arm 714, 716 respectively. The slopingportions accommodate the form of the lower vertebra against which theyare positioned. In the preferred embodiment, the sloping portions are ofabout 30°. However, it is to be understood that sloping portions whichare substantially greater and substantially less than 30° can beincluded and be within the spirit and scope of the invention.

INDUSTRIAL APPLICABILITY

From the above, it is evident that the present invention can be used torelieve pain caused by spinal stenosis in the form of, by way of exampleonly, central canal stenosis or foraminal (lateral) stenosis. Theseimplants have the ability to flatten the natural curvature of the spineand open the neural foramen and the spacing between adjacent vertebra torelieve problems associated with the above-mentioned lateral and centralstenosis. Additionally, the invention can be used to relieve painassociated with facet arthropathy. The present invention is minimallyinvasive and can be used on an outpatient basis.

Additional aspects, objects and advantages of the invention can beobtained through a review of the appendant claims and figures.

It is to be understood that other embodiments can be fabricated and comewithin the spirit and scope of the claims.

We claim:
 1. An implant for relieving pain associated with the spinalcolumn which is positionable between adjacent spinous processes of thespinal column, comprising: a first unit including a body, a guideextending from said body, and a first wing; a second wing; a device thatsecures the second wing to the body; said body adapted for positioningbetween the adjacent spinous processes, with the first wing adapted tobe positionable along first sides of the adjacent spinous processes andthe second wing adapted to be positionable along second sides of thespinous processes and opposite to the first wing; and said guide islocated distally from the first wing; and wherein said guide is shapedso as to be adapted to guide the body between and distract adjacentspinous processes without requiring that the shape of the spinousprocesses be altered, and wherein the guide extends in a direction ofinsertion of the body between the spinous processes; and wherein saidguide is of sufficient length to extend beyond the spinous processeswith the body remaining between the spinous processes.
 2. The implant ofclaim 1 wherein: said first wing has upper and lower portions; saidsecond wing has upper and lower portions; an upper saddle is definedamong the body and the upper portions of the first and second wings; anda lower saddle is defined among the body and the lower portions of thefirst and second wing.
 3. The implant of claim 1 which does not limitflexion of the spinal column while limiting extension of the spinalcolumn.
 4. The implant of claim 1 wherein: said guide has anincreasingly reduced cross section in a direction extending from thefirst wing.
 5. The implant of claims 1 wherein: said body has an ovalcross-section which is substantially perpendicular to said longitudinalaxis.
 6. The implant of claim 1 wherein: along said longitudinal axis,said body has varying cross-sections that are substantiallyperpendicular to said longitudinal axis.
 7. The implant of claim 6wherein: there is a smooth transition between the varyingcross-sections.
 8. The implant of claim wherein: said body has first andsecond end portions and a central portion located between the first andsecond end portions; and from said central portion toward both the firstend portion and the second end portion the varying cross-sections becomelarger.